Among the other unpleasant aspects of having the disorder diabetes mellitus is the need to frequently test one's blood glucose concentration. With current technology a diabetic individual generally must prick his own fingertip or other body part to withdraw blood to determine the blood glucose concentration. The user may be informed directly of the blood glucose value, or the value may be used to calibrate a related device, such as a continuous glucose monitor. But, with the passage of time, continuous glucose monitors often become less accurate.